ACTUATOR ACTUATOR kali_0142 (Mechanical) (OP) 21 Jan 18 08:58 HI respectable friends and sirs/madam. could anyone please explain about actuator and valve torques. BTO RTO ETO BTC RTC ETC MAST i know that abbreviation.just explain? RE: ACTUATOR LittleInch (Petroleum) 21 Jan 18 09:30 The torque on a valve varies during its operation from initial position (B) through the running action (R) to the end position (E). MAST looks like maximum allowable Stem torque. You need this data to match the actuator to the particular valve. A bit more explanation of your issue would help. Remember - More details = better answers Also: If you get a response it's polite to respond to it.